docs: def contains(self, key):
      """Checks if the specified item exists.
  
      Args:
        key: the key of the item to lookup.
      Returns:
        True if the item exists; False otherwise.
      Raises:
        Exception if there was an error requesting information about the item.
      """
      try:
        self._api.objects_get(self._bucket, key)
      except datalab.utils.RequestException as e:
        if e.status == 404:
          return False
        raise e
      except Exception as e:
        raise e
      return True